Device and method for optical coherence tomography in laser material processing processes

Abstract

To provide a device for monitoring a process in laser material processing, comprising a laser generating a light beam, where the light beam may impinge on a lens matrix positioned between a light source and a beam splitter.SOLUTION: The lens matrix may comprise microlenses operable to generate a matrix of light beams from an impinging light beam. Part of the matrix of light beams may be directed to a mirror in a reference arm, and part may be directed to an unknown surface in a measuring arm. The reflection of these beams may be used to generate an interference signal to be evaluated.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] Cross - reference to related applications

[0001] This patent application claims priority and benefit based on German patent application DE10 1022 003 907.9, filed on October 21, 2022, at the Deutsches Patent - und Markenamt. The above - mentioned application is incorporated herein by reference.

[0002]

[0002] The present disclosure relates to devices and methods for optical coherence tomography in laser material processing processes.

Background Art

[0003]

[0003] Aspects of the present disclosure relate to devices and methods for optical coherence tomography in laser material processing processes. Various problems may exist in conventional solutions for optical coherence tomography in laser material processing processes. In this regard, conventional systems and methods for optical coherence tomography can be expensive, cumbersome, and / or inefficient.

Summary of the Invention

Problems to be Solved by the Invention

[0004]

[0004] The limitations and disadvantages of conventional systems and methods will become apparent to those skilled in the art through a comparison of such approaches with some aspects of the methods and systems described in the remainder of the present disclosure while referring to the drawings.

Means for Solving the Problems

[0005]

[0006] Devices and methods for optical coherence tomography are shown in at least one of the figures and / or are described in relation to at least one of the figures and are further fully described in the claims.

[0006]

[0007] These and other advantages, aspects, and novel features of the present disclosure, and details of the embodiments thereof, will be better understood from the following description and drawings.

[0008] Various features and advantages of this disclosure can be more readily understood by referring to the following detailed description, which is taken into consideration in conjunction with the accompanying drawings, where similar reference numerals indicate similar structural elements. [Brief explanation of the drawing]

[0007] [Figure 1]

[0009] This diagram shows the configuration for OCT measurement. [Figure 2]

[0010] This diagram shows the configuration for measurements using OCT. [Modes for carrying out the invention]

[0008]

[0011] The following description provides various examples of semiconductor devices and methods for manufacturing semiconductor devices. Such examples are not limiting, and the scope of the appended claims should not be limited to the specific examples disclosed. In the following description, the terms “example” and “for example” are not limiting.

[0009]

[0012] The figures show a schematic representation of the structure, and well-known features, technical descriptions, and details may be omitted to avoid unnecessarily obscuring this disclosure. In addition, elements in the drawings are not necessarily drawn to a consistent scale. For example, the dimensions of some elements in the figures may be exaggerated compared to others to help understand the examples described in this disclosure. The same reference numeral in different figures represents the same element.

[0010]

[0013] The term "or" means any one or more items in a list linked by "or". For example, "x or y" means any element in the 3-element set {(x), (y), (x,y)}. For another example, "x, y, or z" means any element in the 7-element set {(x), (y), (z), (x,y), (x,z), (y,z), (x,y,z)}.

[0011]

[0014] The terms “equip,” “include,” “possess,” and / or “have” are “non-exclusive” terms that identify the presence of the described feature but do not exclude the presence or addition of one or more other features.

[0012]

[0015] Terms such as “first,” “second,” etc., may be used herein to describe various elements, and these elements should not be limited by these terms. These terms are used solely to distinguish one element from another. Thus, for example, the first element discussed herein may be referred to as the second element without departing from the teachings of this disclosure.

[0013]

[0016] Unless otherwise specified, the term “combined” may be used to describe two elements that are in direct contact with each other, or two elements that are indirectly connected by one or more other elements. For example, if element A is combined with element B, element A may be in direct contact with element B, or indirectly connected to element B by an intervening element C. Similarly, the terms “above” or “on top” may be used to describe two elements that are in direct contact with each other, or two elements that are indirectly connected by one or more other elements.

[0014]

[0017] Optical coherence tomography (OCT) is a technique that can be used for high-resolution cross-sectional imaging. OCT uses light and can be used, for example, to acquire cross-sectional images of tissue structures at the micrometer scale in situ and in real time. The use of OCT in combination with catheters and endoscopes can enable high-resolution intraluminal imaging of organ systems.

[0015]

[0018] OCT can function as a type of optical biopsy and can be a powerful imaging technique for medical diagnosis, for example, for use in ophthalmology.

[0019] OCT can also be used for material processing processes. For example, an OCT configuration may use a single low-coherence light source and detector in combination with a deflection mirror. This technique can generate a single "pixel" that is swept across the entire field that may be of interest for process monitoring. However, in some examples, the speed and quality of the measured data may be limited when advanced optical elements and electronics may be required for data acquisition and processing. According to various embodiments of the present invention, monitoring of material processing processes using OCT can be improved.

[0016]

[0020] For example, microoptical elements can be arranged in the optical path of the OCT between a laser source and a beam splitter, such that an M×N matrix of independent sub-elements corresponding to the number of microoptical elements can be used for measurement instead of, for example, one laser source corresponding to one pixel.

[0017]

[0021] Sub-elements can be combined in a kind of matrix, in the sense of light beams or pixels, and each sub-element can be controlled separately. Light can be projected onto the surface to be measured, and reflected light can be collected. The matrix described above can be understood as a grid of many small lenses that act independently. These may be arranged in rows or lines as required by the particular application.

[0018]

[0022] The use of such a matrix can make it possible to obtain M x N measurement points as snapshots in the sense that they capture instantaneous states. This can be particularly useful for processes where those states change continuously, such as the melting zone in a laser welding process.

[0019]

[0023] While the size of individual pixels in a matrix may be technically limited, individual pixels can be controlled separately or grouped together as needed, making it possible to generate scan programs according to requirements. One such scan program could be a kind of "flash lidar" for meltpools, i.e., a "photograph" that can contain virtually all individual pixels instead of the results of many scans across the entire field of view. This can improve the quality of the results and provide better quality assurance, for example, when welding critical paths for battery components in electric vehicles.

[0020]

[0024] Furthermore, according to various embodiments of the present invention, a camera may be used to record interference signals of such an M×N matrix.

[0025] Figure 1 shows an exemplary configuration for OCT measurement. A light beam 2 may be generated at the light source 1 with low coherence and may collide with a beam splitter 5. From the beam splitter 5, an unknown surface 20 of the sample may be illuminated at the measurement arm 75, and the light may be reflected onto the beam splitter 5 by the unknown surface 20. The light transmitted through the beam splitter 5 may strike the mirror 10 at the reference arm 50 and be reflected back by the mirror 10. Next, the reflected sample beam 76 and reference beam 51 may be combined at the beam splitter 5 and may interfere when the difference in the paths taken by the two beams 76, 51 is less than the coherence length. The interference signal 85 may be recorded by the detector 15 and then evaluated. For evaluation, the detector 15 may be coupled to an evaluation unit (not shown). This may be, for example, a data processing unit.

[0021]

[0026] Moving a mirror along the reference arm 50 (double arrow) along the beam axis of the light beam 2 emitted from the light source 1 while simultaneously measuring the interference signal 85 can enable axial scanning of the unknown surface 20 of the sample.

[0022]

[0027] FIG. 2 shows an exemplary configuration according to various embodiments of the present invention. A lens matrix 4 having an M×N matrix of microlenses can be disposed between the light source 1 and the beam splitter 5. Accordingly, a plurality of light beams 2 can impinge on the beam splitter 5, and thus a plurality of reference beams 51 can impinge on the mirror 10 in the reference arm 50, and a plurality of sample beams 76 can impinge on the unknown surface 20 of the sample in the measurement arm 75.

[0023]

[0028] According to various embodiments of the present invention, infrared light can be emitted from the light source, and thus, for example, a laser diode can be used as the light source.

[0029] A polygon can be used for the microlenses, that is, shapes such as a square, rectangle, hexagon, octagon, etc. can be provided, and thus the microlenses can be arranged without substantially any space between the microlenses. In relation to the optical characteristics of the microlenses, the light rays emitted from the microlenses can be substantially parallel so that a matrix including M×N light rays or light spots can be obtained as a result.

[0024]

[0030] The camera 25 can be used as a sensor instead of a small detector for one beam. The plurality of beams 51, 76 from the reference arm 50 and the measurement arm 75 from the M×N matrix can be correspondingly evaluated in the interference signal 85 which can further correspond to the plurality of M×N beams from the M×N matrix.

[0025]

[0031] Such configurations according to various embodiments of the present invention may result not only in a single point that can be seen and / or evaluated, but also in an area containing a number of pixels M × N corresponding to the matrix.

[0026]

[0032] In laser material processing, the melt pool can change continuously during the ongoing operation. Using the configuration described above, it may be possible to continuously monitor the continuously changing surface of the melt pool or its transient front. According to various embodiments of the present invention, a so-called LiDAR (Light Detection and Ranging) sensor may be used as a camera for this purpose. A monochrome image may be sufficient for the camera, but a camera for color images may also be used. The frame rate may preferably be greater than 10 fps (frames per second).

[0027]

[0033] Methods and their use for monitoring and controlling processes in laser material processing can be realized by various embodiments of the present invention. In addition to image representations of the results of interference signal evaluation, such results may be used to control or optimize the laser material processing process. Individual pixels in the matrix can be controlled individually. This means that they can be moved individually in the X and Y dimensions, if desired. For this purpose, for example, microlenses can be moved accordingly, which can change the position of the light beam and, therefore, further change the position of the relevant pixels in the interference signal.

[0028]

[0034] Therefore, methods according to various embodiments of the present invention can be used to control the processes of laser material processing, and thus ultimately control them. In this case, it can be not only a matter of quality assurance but also a matter of control.

[0029]

[0035] Other aspects, features, and advantages of the present invention will be readily apparent from the following detailed description, which briefly outlines preferred embodiments and models. The present invention may be further realized in other embodiments and different embodiments, and various details thereof may be modified in various obvious aspects without departing from the teachings and scope of the present invention. Accordingly, the drawings and description are intended to be illustrative and not limiting. Further objects and advantages of the present invention are partially described in the following description, partially apparent from the description, or can be inferred from embodiments of the present invention.

[0030]

[0036] While this disclosure includes references to specific examples, it will be understood by those skilled in the art that various modifications may be made without departing from the scope of this disclosure, and that equivalents may be substituted. In addition, modifications may be made to the disclosed examples without departing from the scope of this disclosure. Therefore, it is intended that this disclosure is not limited to the disclosed examples and that it includes all examples that fall within the scope of the appended claims. [Explanation of Symbols]

[0031] 1 light source 2 Light beams 4 Lens Matrix 5 Beam Splitter 10 Mirror 15 Detectors 20 Unknown Surfaces 25 Cameras 50 Reference Arm 51 Reference beam 51 Beam 75 Measuring Arm 76 Sample beams 76 beams 85 Interference signals

Claims

1. A laser that generates a light beam, wherein the light beam collides with a lens matrix located between the laser and a beam splitter, The lens matrix includes an M x N microlens capable of generating an M x N matrix of light beams from the colliding light beams, A beam splitter that directs a first portion of the M×N light beam onto a mirror on a reference arm and a second portion of the M×N light beam onto an unknown surface on a measuring arm, wherein the first portion of the M×N light beam is reflected back from the mirror to the beam splitter, and the second portion of the M×N light beam is reflected back from the unknown surface to the beam splitter, A beam splitter capable of generating an interference signal by interfering the first reflected portion of the M×N light beam with the second reflected portion of the M×N light beam, A detector that receives the aforementioned interference signal and A device for a laser material processing process, wherein the matrix of M × N light beams and, therefore, the matrix of M × N pixels of interference signals can be controlled individually.

2. The device according to Claim 1, wherein the matrix of M x N light beams and, therefore, the matrix of M x N pixels of interference signals can be individually controlled by moving the microlenses.

3. A device according to claim 1 or 2, wherein the detector is a camera.

4. A device according to claim 1 or 2, wherein the detector is a monochrome camera or a color camera.

5. A device according to claim 1 or 2, wherein the microlenses are polygonal such that the microlenses are arranged with substantially no space between them.

6. A device according to claim 1 or 2, wherein the mirror is coupled to a drive unit for moving the mirror in the direction of the beam path of the light beam.

7. A device according to claim 1 or 2, further comprising a unit for evaluating the detected interference signal, wherein the detector is connected to the unit for evaluating the data.

8. A method for monitoring an unknown surface in a laser material processing process, A step of generating a light beam using a laser, wherein the light beam collides with a lens matrix located between the laser and a beam splitter, A step of generating a matrix of M x N light beams from the colliding light beams using the lens matrix which includes M x N microlenses, A step of using the beam splitter to direct a first portion of the M×N light beam onto a mirror on a reference arm and a second portion of the M×N light beam onto an unknown surface on a measuring arm, wherein the first portion of the M×N light beam is reflected back from the mirror to the beam splitter, and the second portion of the M×N light beam is reflected back from the unknown surface to the beam splitter. The beam splitter comprises the step of generating an interference signal by interfering the first reflected portion of the M x N light beam with the second reflected portion of the M x N light beam, The steps of receiving the interference signal in the detector and A method comprising the following, wherein the matrix of M × N light beams and, therefore the matrix of M × N pixels of the interference signal can be controlled individually.

9. A method according to claim 8, further comprising the step of individually controlling the matrix of M x N light beams and, therefore, the matrix of M x N pixels of the interference signal by moving the microlenses.

10. A method according to claim 8 or 9, wherein the step of receiving the interference signal is performed by a camera.

11. A method according to claim 8 or 9, wherein the received interference signal is evaluated by an evaluation unit connected to the detector.

12. A method according to claim 11, wherein the results of the evaluation are shown as an image on a display.

13. A method according to claim 8 or 9, wherein the individually controlled light beams and pixels may include motion in the X or Y direction.

14. A method according to claim 11, wherein the evaluation is used to control a process in a laser material processing process.

15. A method according to claim 8 or 9, wherein the laser material processing step is a welding step or a material cutting step.

16. A method according to claim 8 or 9, for monitoring the joining process when joining workpieces with a laser beam.

Images